1. Field of the Invention
This invention relates to a recording apparatus, and more particularly, to a recording apparatus in which a carriage with a recording head on it is reciprocated by a single driving source and, at the same time, recording material is fed to the recording head.
2. Description of the Prior Art
Heretofore in recording apparatus, a single driving motor is rotated in the forward or reverse direction, and such rotation is converted into reciprocating movement of a print head carriage (in a printing direction or return direction) using a transmission mechanism such as a gear, pulley or the like. Then, when printing is complete and recording material (for example, paper) is to be fed, the rotation of the motor is transmitted to a paper-feeding roller using a one-way clutch. Paper feeding is performed by rotating the paper-feeding roller only when the carriage is moving in the return direction. In feeding the paper by one line, the carriage has to travel over the distance corresponding to an entire line, irrespective of the number of characters or columns to be printed. It is difficult to achieve high-speed movement of the carriage because the transmission mechanism becomes complicated. In addition, if it is desired to perform continuous paper feeding without printing, or to print lines with a small number of columns per line, the carriage still has to travel over the distance covering one line. This decreases the paper-feeding speed and printing speed.
In order to solve such problems, there are two mechanisms disclosed in Japanese Patent Provisional Publication No. 57-89982 (1982). In the first, paper is fed by one line using a cam to limit the driving range of the paper-feeding roller, without requiring the carriage to reciprocate over the distance covering a whole line. In the second, paper is fed by one line even when the carriage is returned from an arbitrary printed column, by using a conventional spring clutch and a simple transmission mechanism, without requiring electric control means such as an electromagnetic clutch, an electromagnet or the like.
This first conventional approach will be explained in more detail with reference to FIGS. 1 A, 1 B and 1 C. These figures show a bubble-jet recording apparatus for performing serial recording. In these figures, there are shown a frame 1 and a recording head 2 for recording by discharging ink using the bubble-jet method. A carriage 3 carries the recording head 2, and is reciprocated along a guide shaft 4. Both ends of a wire are fixed to the carriage 3, and the wire 5 is stretched between pulleys 6. A stepping motor 7 can drive the wire 5 via a gear 7A to reciprocate the carriage 3.
A shaft-type cam 8 has a continuous guide projection 8A, as shown in FIG. 2, which is fitted in a groove (not illustrated) in the carriage 3. Further, a clutch spring 9 and a clutch gear 10, one end of which is anchored to and co-operates with the clutch spring 9, are fitted in the home-position end of the cam 8 (designated H in FIG. 2). In these figures, when the cam 8 is rotated clockwise, the clutch gear 10 and the cam 8 are engaged via the clutch spring 9, and it is possible to rotate the clutch gear 10 clockwise. When the cam 8 is rotated counterclockwise, the clutch spring 9 does not engage with the cam 8, and the clutch gear 10 is not rotated.
Now, in FIG. 1 B, when the carriage 3 is moved backward from left to right, that is, toward the home position H, it first reaches the position G shown in FIG. 2. The cam 8 will thereafter start rotating clockwise in accordance with the shape of the guide projection 8A, and this movement continues until the carriage 3 reaches the home position H. During that time, the clutch gear 10 is also rotated clockwise. The clutch gear 10 is configured, as shown in FIG. 1 B, so as to drive a sheet-feeding gear 12 via an idle gear 11. The clutch gear 10 thus rotates a paper-feeding roller (not illustrated), and it is possible to feed a recording sheet which is held between the feeding roller and a pinch roller 13.
During forward movement of the carriage away from homeposition H, recording is performed by the recording head 2 and the cam 8 is rotated counterclockwise as the carriage moves from position H to position G. However, as described above, the clutch gear 10 is not rotated, and hence the paper-feeding roller is not driven.
By such a recording apparatus, when the stepping motor 7 is switched on and the carriage 3 is at the home position H, the carriage 3 is moved to the left by the motor 7 and, in synchronization with the carriage movement, ink-discharge signals are selectively supplied to the recording head 2 via a flexible cable 14, and thus recording is performed. When recording for one carriage scanning is completed, the carriage 3 is returned to the home position by reverse rotation of the stepping motor 7. When the carriage 3 returns to a predetermined position (as described above, the position G of the cam 8), the clutch gear 10 starts rotating, drives the feeding roller, and thus sheet feeding is performed. When continuous, rapid printing feeding is required without sheet, it can be achieved by reciprocating the carriage 3 between the positions G and H shown in FIG. 2. Further, when the number of columns to be recorded is small, it is possible to perform sheet feeding by returning the carriage 3 from the position of the last printed column toward the right.
In this conventional recording apparatus, however, the load on the stepping motor is increased when the paperfeeding roller is driven by the cam 8, and the torque characteristic of the motor at that range should be large. This results in a complicated control. Moreover, when the paper-feeding roller is driven by the cam 8, especially if the gear 10 is provided with a ratchet, violent vibration and noise can occur. Further, since the number of components in this arrangement is large, there are reliability problems. Thus, this conventional apparatus has many problems to be solved.
Another approach is disclosed by Japanese Patent Provisional Publication No. 59-145175 (1984). The rotation of a motor is converted into movement of a carriage by means of a lead screw or the like. When the carriage is located outside the printing range, the rotation of a cam member is transmitted to a paper-feeding roller via a clutch provided at an end portion of the cam member. However, this approach also requires a complicated configuration, and has the same problems as those described above.
This second conventional approach will be explained in more detail with reference to FIGS. 3 and 4.
FIG. 3 shows a driving motor 21, such as a pulse motor or the like, connected to a carriage-driving shaft 25 via gears 22, 23 and 24. The carriage-driving shaft 25 is rotatable in both forward and reverse directions in accordance with the rotation of the motor. A carriage 27 is slidably supported along the carriage-driving shaft 25. A printing head 26 is fixed to the carriage 27, and a worm gear 28 is attached to the carriage 27. The worm gear 28 is secured to and rotated by the carriage-driving shaft 25.
Consequently, when the carriage-driving shaft 25 is rotated counterclockwise (viewing FIG. 3 from the right), the worm gear 28 is also rotated counterclockwise. By the meshing between the worm gear 28 and a rack gear 31, the carriage 27 and, accordingly, the printing head 26, are moved in to the right, that is, in the printing direction, along the carriage-driving shaft 25. At the same time printing is performed by the printing head 26.
Further, the above-described carriage-driving shaft 25 is connected to a paper-feeding driving shaft 35 via gears 32, 33 and 34, so that the paper-feeding driving shaft 35 is also rotated counterclockwise with the shaft. Counterclockwise rotation of the paper-feeding driving shaft 35 also rotates a boss 36, and a friction plate 41, counterclockwise. Hence, a projection 30 is moved counterclockwise, and with that movement a lever 29 is rotated clockwise, and a claw on the lever 39 is disconnected from a clutch cam 38. In this case, when the boss is rotated counterclockwise (viewing FIG. 4 from the right), such rotation is not transmitted to a cam gear 39, or to a paper-feeding roller 40, since this rotation is in a direction that loosens a spring 37 from around the boss 36.
Then, when one line of printing is completed, rotation of the carriage-driving shaft 25 is reversed, and the printing head 26 returns to the left, that is, in the reverse direction. By the reverse rotation of the carriage-driving shaft 25, the paper-feeding driving shaft 35 starts rotating clockwise (viewing FIG. 3 from the right). This rotates the boss 36 and the friction plate 41 in a clockwise direction. However, since the claw of the lever 29 is disconnected when the projection 30 starts moving, the clutch cam 38 can be rotated clockwise. On the other hand, when the boss 36 is rotated clockwise, the spring 37 is clamped to the outer circumference of the boss, and torque is transmitted to the cam gear 39 to perform paper feeding.
Further, when the paper-feeding driving shaft 35 continues rotating clockwise (viewing FIG. 3 from the right), the projection 30 is moved to the end of its rotation in the clockwise direction. Hence, the claw of the lever 29 also returns to an engaging position with the clutch cam 38. When the clutch cam 38, which thus rotates practically as one body with the cam gear 39, completes one revolution, further rotation is prevented by the claw of the lever 29. When a force in the counterclockwise direction (viewing FIG. 4 from the right) is applied to the clutch cam 38, the spring 37 is loosened around the boss 36. Hence, the rotation of the boss 36, and the paper-feeding driving shaft 35, is no longer transmitted to the cam gear 39.
Thus, paper feeding can be performed by transmitting only the first reverse revolution of the paper-feeding driving shaft 35 to the cam gear 39 and the paper-feeding roller 40, when the printing head 26 is shifted from traveling in the printing direction to the return direction. When paper feeding is performed, by the rotation of the paper-feeding roller 40, a lever 42 is rotated counterclockwise by the action of the cam gear 39, and a platen 43 is separated from the printing head 26, so that paper feeding is smoothly performed.
In this second conventional apparatus, however, there are problems in that the apparatus is large and higher in cost.